University of Amsterdam researchers found that ancient Egyptians employed what Phys.org calls a "clever trick" to facilitate the pyramids' construction: They likely wet the sand along the path they dragged their sleds, which were laden with pyramid stones weighing some 2.5 tons, reports Gizmodo.

This greatly lessened the power needed to pull the sledge from the quarry to the construction site—so much so that the number of people needed to pull the sledge could be cut in half. Assuming the right amount of water was used, that is.

As the researchers write, "liquid bridges start to form between the grains when water is added. Once there is enough water, these bridges act like glue, keeping the grains in place.

When the "correct amount" of water is applied, the wet sand becomes about two times as stiff as dry; this prevents the sand from amassing in front of the sledge, which allows it to glide more easily.

But add too much water and those bridges "start to merge and disappear."

This trick was "staring [researchers] in the face all along," notes Gizmodo: A wall painting found in an Egyptian tomb shows slaves hauling a sled loaded with a huge statue; in front of them is a person pouring water into the sand.

(It's not the only big Egyptian discovery of the week: This one involves Jesus.)

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